1420965-47-4Relevant academic research and scientific papers
A study on the diastereoselective synthesis of α-fluorinated β3-amino acids by α-fluorination
Peddie, Victoria,Abell, Andrew D.
, p. 2460 - 2473 (2013/03/13)
The treatment of a β3-amino acid methyl ester with 2.2 equiv. of lithium diisopropylamide (LDA), followed by reaction with 5 equiv. of N-fluorobenzenesulfonimide (NFSI) at -78° for 2.5h and then 2h at 0°, gives syn-fluorination with high diastereoisomeric excess (de). The de and yield in these reactions are somewhat influenced by both the size of the amino acid side chain and the nature of the amine protecting group. In particular, fluorination of N-Boc-protected β3-homophenylalanine, β3-homoleucine, β3-homovaline, and β3-homoalanine methyl esters, 5 and 9-11, respectively, all proceeded with high de (>86% of the syn-isomer). However, fluorination of N-Boc-protected β3-homophenylglycine methyl ester (16) occurred with a significantly reduced de. The use of a Cbz or Bz amine-protecting group (see 3 and 15) did not improve the de of fluorination. However, an N-Ac protecting group (see 17) gave a reduced de of 26%. Thus, a large N-protecting group should be employed in order to maximize selectivity for the syn-isomer in these fluorination reactions. Copyright
